


The Anatomy and Physiology of a Dragonlord

by pinlilli



Category: Merlin (TV)
Genre: Arthur Knows About Merlin's Magic, Big dick merlin, Bottom Arthur Pendragon (Merlin), Established Relationship, First Time, Knotting, M/M, Multiple Orgasms, Plot What Plot/Porn Without Plot, Size Kink, Top Merlin, True Mates
Language: English
Status: Completed
Published: 2018-04-12
Updated: 2018-04-12
Packaged: 2019-04-21 20:43:31
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,257
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/14293068
Author URL: https://archiveofourown.org/users/pinlilli/pseuds/pinlilli
Summary: "What in the hells are you doing, Merlin?" Arthur asks. "It feels like you're trying to fit your bloody foot inside me."a kinksofcamelot fill for the prompt: "A little-known aspect of Dragonlord anatomy is their ability to knot when they have found their lifelong mate. Merlin and Arthur discover this the hard (lol) way."





	The Anatomy and Physiology of a Dragonlord

**Author's Note:**

> This turned out not at all like I had intended, but I hope it makes for an enjoyable read nonetheless. Enjoy!

Merlin pulls his fingers out of Arthur and wipes them on the sheets beneath them. Gives one last kiss to Arthur’s belly. “Turn around,” he says.

Arthur scrambles to obey and thinks finally, _finally_. He props himself up on his knees and elbows, cock dangling hard and heavy between his legs. The air is cool on his slick and ready hole. He’s been dripping with precome for the better part of the hour. Merlin had taken his sweet time preparing him, would probably have been content to finger Arthur for the rest of the night, if Arthur hadn’t batted at his hand and ordered Merlin fuck him.

Merlin steadies him with a hand on his hips, fingers digging into the meat there. Arthur’s breath hitches at the first press of Merlin’s cock against his hole. Instinctively, he clenches up. Merlin rubs the head of his cock over his hole until he’s relaxed again. And then, he begins to push forward.

Arthur squeezes his eyes shut against the intrusion. He wants this—gods, he wants this. Has spent an entire year trying to sneak peeks of Merlin’s cock, imagining what it might feel like inside him. It was a fantasy that had kept him occupied during the long hours spent in council, and on the nights he was feeling lustful and alone. But he hadn’t known it would feel like this; Merlin looked big, but not _this_ big. The stretch has him breaking out in sweat. A droplet of it slides down his neck and collects at the dip of his collarbone.

“Are you quite finished yet, Merlin?” Arthur grits out.

Merlin laughs, breathless. He smooths large palms up and down Arthur’s back, soothing. “Just a little more, sire.”

“A little more” feels like the entire goddamn hilt of a sword. By the time Merlin’s pelvis meets his arse, Arthur can hardly see straight. The pressure is astounding, stretching him out from all sides. 

He clenches experimentally around Merlin’s girth and his prick jerks, blurting out another line of wet. “Oh gods,” he moans, letting his head drop to hang between his shoulders. He spreads his knees wider and arches his arse up, as though it’ll help him take Merlin’s cock better. 

Merlin dips down to kiss the bump of his spine, panting softly into Arthur’s skin. “This okay?”

“Yes,” Arthur grunts. Better than okay. “Now move.”

Merlin, for once, obeys him without his usual snark.

Arthur curls his fingers into the blankets beneath him. Catalogues every blood-hot inch of Merlin as he slides back inside. He can’t help the throaty moans that escape him with every thrust; Merlin is thick enough that every movement brushes against the bundle of nerves deep inside him.

“Yes, gods, Merlin. Just like that,” he moans. “There are things you can do right, after all.”

Merlin delivers a sharp, reprimanding smack to his arsecheek that has him crying out with shock. The only reason why he doesn’t yell at Merlin for that is because at that exact moment, Merlin snaps his hips forward hard enough for Arthur to see stars. It could also have something to do with the fact that the sting left behind by Merlin’s palm is actually rather pleasant.

“Prat,” Merlin says. “You can’t even be nice to me when I’m making love to you.”

In response to those words, Arthur rocks back to meet Merlin’s thrusts. Now that he has this, he’ll never understand why they waited so long. (He knows, of course, that he spent years trying to deny himself because no prince should feel this way about his manservant; and Merlin was waiting for him to make the first move, until he realised that Arthur Pendragon was a coward when it came to certain things).

Maybe, if he weren’t in such a delirious state of mind, he would be embarrassed that he’s been pushed this close without a single touch to his cock. But Merlin is making him feel so good—grinding his pelvis in filthy circles while buried deep to let Arthur feel every inch of him—that Arthur can’t bring himself to care. 

The thing is though, when Arthur says, “just like that”, that’s exactly what he means. It doesn’t mean start pounding the ever-loving fuck out of him. He certainly isn’t asking to be stuffed with more cock. Somehow, Merlin seems to be doing just that. Merlin is swelling inside him, his already thick cock growing engorged—and wetter, slicker, at the tip, Arthur notices. 

It’s the flared base of Merlin’s cock that Arthur can’t make sense of. He feels something bulbous bumping against his hole with every movement, trying to sneak its way past the tight ring of muscle alongside the rest of Merlin’s cock.

It’s _huge_. 

Enough to scare Arthur a little, though that’s mostly because he doesn’t know what it is. 

"What in the hells are you doing, Merlin?" Arthur asks. "It feels like you're trying to fit your bloody foot inside me."

Merlin chokes out a noise halfway between a snort and a moan. “I would never, sire.”

“Well, what is it then?” Arthur demands. “Because it seems to me like you’re trying to split me in half. If I die like this, my father will have you executed, you know. I won't even be around to save your sorry behind."

And Merlin, the bastard, laughs at him. “It - ah - appears I am knotting you?” 

"Appears?" Arthur questions. "So you're not sure what it is exactly you are doing to my arse?" 

Merlin has stopping rocking his hips now, and Arthur becomes all too aware of his length pulsating inside him. He amends, "I'm knotting you. I mean, I’m trying to. That is, I’d like to, but I wouldn’t, if you didn’t want it, too.”

Arthur thinks about this for a moment and finds that he doesn’t understand. To his credit, it is hard to think when he is impaled on Merlin’s cock. "What? Knotting like a wolf, you mean?"

"Like a wolf," Merlin confirms. 

First magic and now this? "If you’re hiding ears as well, now would be the time to tell me,” Arthur says. Cranes his neck around to check and swallows hard at the sight. Merlin looks gorgeous and devastating. The colour is high in his cheeks, the flush creeping down his neck and over his heaving chest. His molten eyes gleam gold in the candle-lit room and his brows are drawn together, as though it physically pains him to remain still while he’s sheathed inside Arthur’s body.

“No. No ears,” Merlin says. Hesitantly, he asks, “Do you want me to stop?”

“No, I don’t want you to stop, you clotpole. Just use more oil,” Arthur huffs and purposefully clamps his arse down on Merlin. Because Arthur, god help him, finds he likes that Merlin is a little too big for him to take comfortably. That he has to struggle and squirm. He could attribute it to the fact that a Pendragon never balks from a challenge, but he knows it’s not that.

The truth is, he likes feeling so full that he can hardly breathe with it. Every time Merlin shoves into him, it punches all the air out of his lungs.

Behind him, he hears Merlin fumble with the jar of oil, and then he feels it drizzling down his arse. 

Merlin splays out his hands on Arthur’s arsecheek, the tip of thumbs teasing at his entrance and spreading them further apart. The additional stretch has him moaning. He can feel those eyes on him, staring, and it makes his cheeks burn. 

“I don’t know if I’m going to fit,” Merlin says. He presses a fingertip to Arthur’s entrance, manages to wedge it in alongside his cock after some coaxing.

Coming from anyone else, Arthur would think it was a boast. But from sweet, gentle Merlin, who had tenderly kissed Arthur’s belly while opening him up with his fingers… He knows Merlin worries about hurting him. “I can take it,” Arthur grunts. “I’ve endured worse.”

“I would hate to be the cause of any pain you experience,” Merlin murmurs, crooking his finger and pressing at his walls. “You’ll tell me if it’s too much, won’t you?”

“Yes, yes, Merlin. Just get on with it!”

But Merlin won’t be rushed, not for this. Only once has he deemed Arthur ready, does he grasp Arthur by his hips and proceed to force in his knot.

“Oh, gods, _ohh_ ,” Arthur moans as the bulge at the base of Merlin’s cock begins to breach him. Tears prickle in the corners of his eyes when he reaches the widest part of his knot. The stretch is excruciating and overwhelming and Arthur struggles to breathe around it. It’s pure, electrifying sensation when Merlin’s knot pop insides him. His hole flutters around the intrusion, throbbing and aching with a heat that flushes through his entire body. 

And then Merlin starts to fuck him with it, knot popping out of his arse and then back in again. Arthur’s fat prick swings between his legs as Merlin rocks into him, slow at first, and then with increasing speed when Arthur begs for it. Every time Merlin drives into him, he’s shoved forward onto the mattress and Merlin has to reel him onto his cock. The sound their bodies make when Merlin plunges into him is downright obscene, wet and squishing, not unlike churning butter.

“I wish you could see yourself like this, Arthur,” Merlin says. “Taking me so well.” His voice is strained and reverent. Of all things, that is what makes Arthur hide his face in his pillow, shy. He wants to tell Merlin to shut up but finds that he can’t, his vocal chords otherwise occupied by him moaning like a cheap whore from a brothel in the lower town. 

His orgasm builds and roils low in his gut. With one last thrust, the crest of his pleasure breaks and he comes with a shout, spilling onto the fine sheets beneath him.

Merlin groans loudly, folding over Arthur so that his forehead is resting on the nape of his neck. With one final shove, his knot catches on Arthur’s hole and locks them together, swelling even further once it’s inside him. Merlin’s cock twitches and then he’s coming too, his hot release flooding through Arthur’s inner walls. There’s so much of it, spurt after spurt spraying up his insides.

Arthur shudders, bloated with Merlin’s knot and come.

Merlin puts a hand on his lower belly, rubbing his thumb over the swell of it. “Oh gods, Arthur,” he groans. “I can feel myself inside you.” He presses down on Arthur’s belly and it makes everything inside him go all tight. It’s been mere seconds since his last orgasm but Arthur can’t help it. With a low moan, he shoots all over himself, cock jerking helplessly.

“Arthur, did you—” Merlin cuts himself off in favour of nuzzling and kissing Arthur’s sweaty temple, comforting, and Arthur realises then that he’s whimpering. His cheeks are wet from tears of exertion.

“Shh, my prince,” Merlin croons. Manoeuvres them so that they can lie on their sides, with his arm wedged beneath Arthur’s ribs. Merlin is trying to be careful, but his knot is so fat that even the slightest of movements is enough to set him off.

Arthur comes yet again, thighs shaking, every single goddamn speck of his being shaking as he loses all control of his muscles for one terrifying moment. He curls into himself, hole spasming around Merlin’s cock. There’s not enough breath left in his chest to make even the smallest of noises. His spent cock manages nothing more than a weak dribble, leaving him drained and boneless.

* * *

Later, when Arthur has relearned how to breathe and his world doesn’t feel fuzzy around the edges, he and Merlin lie together in bed. Merlin has finally softened to slip out of him and it leaves him loose and sloppy. He knows that Merlin’s come is trickling out of his hole because it tickles as it runs down the valley of his arse, and also because Merlin won’t stop talking about it, saying things like, “Oh gods, Arthur, you’re dripping here”, and then pushing it back inside with a thumb. The possessive gesture has Arthur shivering and mewling weakly; his hole is tender and puffy and sore.

Arthur’s ability to form coherent sentences comes back to him slowly. The first thing out of his mouth is, “I’ve never seen your cock do that before.” They’ve given each other handjobs before and he’s never noticed anything peculiar about Merlin’s prick, only that it was both thicker and longer than his own.

“Neither have I,” Merlin says.

“I didn’t know it was possible. You don’t suppose mine will do the same if I fuck you instead?” Arthur muses.

Merlin laughs quietly. “I don’t think so.”

“Does it have something to do with your magic?”

Merlin hesitates before answering, “Something to do with being a dragonlord, I think. I’m - ah - supposed to be able to knot my true mate.” 

“Oh,” Arthur says. 

Merlin says quickly, “Or so I’ve heard. Who knows if there’s any truth to it, though.”

He turns around in Merlin’s arms so they’re face to face. Merlin’s eyes are so very blue and it makes Arthur’s heart flop over in his chest. His poor manservant looks scared, as though Arthur might refuse him, when Arthur has never denied him for anything. He says, “No. That’s good, since I do love you quite a lot.”


End file.
